Batuan metamorfik.pptx

8/10/2019 Batuan metamorfik.pptx

1/78

Metamorfisme dan

batuan metamorfik


2/78

PREEXISTING

ROCKS

BATUAN

METAMORFIKT, P, CHEMICAL

FLUIDS

METAMORFISME

CONTACT

REGIONAL/

DYNAMIC

CHANGES

TEXTURE

MINERALOGY

LINEATION

FOLIATION

NONFOLIATED

HOW

WHERE

HOW

WHERE

JENIS BATUAN

& CIRI KEJU-

RUTERAAN

JENIS


3/78

Metamorphism means

"changed form (berubahbentuk)


4/78

Kitar batuan (Rock cycle)


5/78

CYCLE


6/78

Batuan Metamorfik terjadihasil drpd perubahan suhu,

tekanan dan bendalir kimia

Agents of Metamorphism

Changes occur because of:

Heat

Pressure

Chemical fluids


7/78

Perubahan suhu:

Geothermal gradient

Temperature increases with depth ata rate of 20 - 30 degrees C per km inthe crust.

Ultimate source of the heat?Radioactive decay. Increase oftemperature and pressure with depthcausesRegional Metamorphism

Metamorfisme Rantau)Heat may come from large bodies ofmolten rock rising under a wide

geographic area.


8/78

Metamorfisme sentuh

Intrusions of hot magma can

bakerocks as it intrudes them.

Lava flows can also bake rockson the ground surface. Lava or

magma in contact with other

rock causes ContactMetamorphism.

Hornfelsis a common contact

metamorphic rock.


9/78

CONTACT


10/78


11/78

Contact

metamorphismContact metamorphism

along a narrow (approx. 1

meter wide) diabase dike in

the Deep River Basin ofNorth Carolina. Diabase

weathers tan. Contact

metamorphic aureole rocks

(hornfels) are gray. Hostrocks are red siltstones


12/78

Metamorfisme Rantau

Pressure Burial Pressure. Pressure increases withdepth due to the weight of the overlyingrocks. A cubic foot of granite weighs 167.9pounds. Increase of pressure andtemperature with depth causes RegionalMetamorphism. Regional metamorphismoccurs at depths of 5 - 40 km.

Tectonic pressures associated withconvergent plate boundaries andcontinental collision also cause Regional

Metamorphism. Pressure along fault zones causes Dynamic

Metamorphism, the crushing and ductileflow of rock. Rocks formed along faultzones are called mylonites


13/78

REGIONAL


14/78

Continental collision


15/78


16/78

3 Chemical Fluids

In some metamorphic settings, newmaterials are introduced by the action ofhydrothermal solutions(hot water withdissolved ions). Many metallic ore depositsform in this way.

Hydrothermal solutions associated with

magma bodies Black smokers- Sea water percolates

through newly formed oceanic crust,dissolving out metallic sulfide minerals. Thehot sea water rises along fractures and

pours from vents in the seafloor as blackclouds of dark mineral-rich water. Sulfideminerals (such as pyrite, sphalerite, andgalena) and copper precipitate when the hotwater comes in contact with cold sea water


17/78

HYDROTHERMAL


18/78

How do rocks change?

Metamorphism causes changes in:

1 Texture (definition: shape, sizeand orientation of mineral

grains in the rocks)

2 Mineralogy (chemicalcomposition)


19/78


20/78

FOLIATION


21/78

FOLIATION


22/78

STRESS


23/78


24/78

Foliasi


25/78

Texture

The processes of compactionand

recrystallizationchange thetexture of rocks (shape, size andorientation) duringmetamorphism.

CompactionThe grains move closertogether.The rock becomes more

dense.Porosity is reduced. Note:this is engineering parameter

Example: clay to shale to

slate


26/78

Recrystallization

Growth of new crystals. No changesin overall chemistry. New crystalsgrow from the minerals alreadypresent. A preferred orientation of

minerals commonly develops underapplied pressure. Platy or sheet-likeminerals such as muscovite andbiotite become orientedperpendicular to the direction offorce. This preferred orientation iscalled foliation.


27/78

Metamorphic

Textures

Foliation is a broad term referring to thealignment of sheet-like minerals. Types offoliation:

Schistosity- alignment of large mica flakes, as

in a mica schistderived from themetamorphism of shale.

Slaty cleavage- alignment of very fine-grainedmicas, as in a slatederived from themetamorphism of shale.

Phyllitic structure- alignment of fine-grainedmicas, as in aphyllite.

Gneissic banding- segregation of light and darkminerals into distinct layers in the rock, as in a

gneiss


28/78

Lineation

refers to the alignment of

elongated, rod-like minerals

such as amphibole, pyroxene,tourmaline, kyanite, etc.

Lineation is a texture commonly

seen in the metamorphic rockamphibolitederived from the

metamorphism of basalt


29/78

Non-foliatedor granular

metamorphic rocks

are those which are composedof equidimensional grains such

as quartz or calcite. There is nopreferred orientation. Thegrains form a mosaic.Examples: quartzitederived

from the metamorphism ofquartz sandstone, and marblederived from the metamorphismof limestone or dolostone.


30/78

Note: Not all quartzites andmarbles are pure. Some containimpurities that were originallymudinterlayered with or mixed

with the original quartz sand orlime mud. These clay impuritiesmetamorphose to layers ofmicas or other minerals, which

may give marble (in particular) abanded, gneissic appearance, orwhich may give a slight foliationto some quartzites


31/78

Foliated metamorphic

rocks

As shale is subjected to

increasing grade of

metamorphism (increasingtemperatures and pressures), it

undergoes successive changes

in texture associated with anincrease in the size of the mica

grains


32/78

Slate

very fine grained rock.Resembles shale. Has slaty

cleavage which may be at an

angle to the original bedding.Relict bedding may be seen on

cleavage planes. Often dark gray

in color. "Rings" when you strike

it. (Unlike shale, which makes adull sound. Temperature about

200 degrees C; Depth of burial

about 10 km.


33/78

slate


34/78

Phyllite

fine-grained metamorphic rock.

Has a frosted sheen, resembling

frosted eye shadow. This is nocoincidence. Cosmetics

commonly contain ground up

muscovite (ground to a sizesimilar to that occurring

naturally in phyllite.)


35/78

phyllite


36/78

Schist

metamorphic rock containing abundant

obvious micas, several millimeters

across. Several types of schist may be

recognized, based on minerals whichmay be present:

mica schist

garnet schist

chlorite schist

kyanite schist

talc schist


37/78

schist


38/78


39/78

gneiss


40/78

gneiss


41/78

Migmatite

a very high grade metamorphic

rock that has been subjected to

such high temperatures that it has

partially melted. It is intermediate

between the metamorphic and the

igneous rocks. Look for swirled

banding. The light colored

minerals have undergone melting

and flow. The dark colored

minerals have been contorted by

flow. Example - the Lithonia

Gneiss in the area southeast of

Atlanta


42/78

migmatite


43/78

non-foliated and weakly foliated)

metamorphic rocks

Marble- fizzes in acid because

its dominant minerals is calcite

(or dolomite). The parent rockis limestone (or dolostone).

( )


44/78

Marmar (Marble)


45/78

Quartzite/kuarzit

interlocking grains of quartz.

Scratches glass. The rock

fractures through the grains(rather than between the grains

as it does in sandstone). The

parent rock is quartz sandstoneHardest rock known

UCS


46/78

quartzite


47/78

Others

Metagraywacke-

metamorphosed graywacke or"dirty sandstone".

Metaconglomerateand

stretched pebble

metaconglomerate- the parent

rock is conglomerate. The clasts

are fairly easily recognized. Maybe more difficult to recognize if

the clasts have been stretched


48/78

Hornfels

A fine-grained, tough, dense,

hard, massive rock. Usually (but

not always) dark in color. Finergrained than basalt, which it

may superficially resemble. This

rock forms throughcontactmetamorphism. The parent rock

is commonly siltstone or basalt,

but may be other types of rock


49/78

Serpentinite

A dark green, dense, tough,massive, hard rack. May contain

veins of asbestos. The parent

rock is peridotite, an ultramaficrock

ultramafic: lack/low amount of

SiO2, Fe, Mg (bandingkan dgnjadual pengelasan batuan

igneus)


50/78

serpentine


51/78

Soapstone

(sometimes called steatite) - a soft,easily carved rock with a slippery

feel because it contains talc and

chlorite. The parent rock isperidotite (ultramafic), probably

with more water associated with it

than in the formation ofserpentinite. Example - Soapstone

Ridge southeast of Atlanta


52/78

Metabasalt

(sometimes called greenstoneif

massive and green, or

greenschistif foliated andgreen) - the green color comes

from chlorite (soft and bluish

green) and epidote (pea green).The parent rock is basalt. The

grade of metamorphism is LOW


53/78

Amphibolite

Abundant amphibole is present;

may be lineated. Usually black.

The parent rock is basalt. Thegrade of metamorphism is

HIGH. Has been subjected to

higher temperatures andpressures than metabasalt,

greenstone, or greenschist.


54/78

Mylonite

A dynamic metamorphic rock

which forms along fault zones

l it


55/78

mylonite

Mylonite along the Linville Falls Fault, Linville Falls,

NC. Relatively undeformed conglomeratic quartzite

lies above the layered mylonite zone


56/78

Mineral changes in

metamorphic rocks

Recrystallization- rearrangement ofcrystal structure of existing minerals.Commonly many small crystals mergeto form larger crystals, such as the

clay in shale becoming micas inslate, phyllite, and schist. Note thechemical compositions of clay andmuscovite.

Also, fine-grained calcite in limestonerecrystallizes to the coarse-grainedcalcite mosaic in marble


57/78


58/78


59/78

Kyanite

sky blue bladed minerals with

differential hardness. Scratch

lengthwise with a knife or nail,but not sideways


60/78

kyanite

Chlorite - dark bluish green, soft. Fe, Mg


61/78

Chlorite dark bluish green, soft. Fe, Mg

Talc- white or pale green and soft.

Graphite- metamorphosed carbon

Tourmaline- commonly black. Formselongated crystals with a roundedtriangular cross-section. Can see atStone Mountain.

Asbestos- fibrous mineral. Commonlylight greenish. Occurs in veins (seemsto fill a crack) with the fibers orientedperpendicular to the edged of the vein.Associated with lung diseases.

Mesothelioma and asbestosis. Found inserpentinite. "Serpent rock" name dueto snake-like veins of asbestos.

Micas- muscovite (silvery), biotite(darkbrown), phlogopite(light brown)


62/78

Batuan metamorfik boleh digunakansebagai tanda aras suhu dan tekanan

dalam bumi

In regional metamorphic terranes, the

temperature and pressure regime isindicated by the distribution ofmetamorphic minerals across a large area.Low metamorphic grade(low temperaturesand pressures) - about 200 degrees C

Slate and phyllite chlorite

muscovite

biotite

Metamorphic index minerals


63/78


64/78

High metamorphic grade- 800

degrees C (verging on melting)Gneiss and migmatite

sillimanite

Know which minerals are themetamorphic index minerals.

Know which ones are

characteristic of low,intermediate, and high

metamorphic grades

FACIES GRADE


65/78

FACIES GRADE

FACIES


66/78

FACIES


67/78

pandangan

Jurutera bahan banyakmenggunakan bahan ini untuk

membuat bahan baru => bahan

termaju (advanced materials),

composite materials,

nanomaterials

Keadaan makmal cuba

disimulasikan seperti yangditemui di dalam bumi

sistem berbeza: open vs closed


68/78

Mi l t d t d


69/78

Mineral yg terdapat pada

zon metamorfik

REGIONAL


70/78

foliation

Slate schist gneiss texture

Gran lar te t re as in


71/78

Granular texture as in

quartzite

Rumus


72/78

Changes that occur in the

transformation to becomemetamorphic rocks


73/78

ENGINEERINGPROPERTIES

1. POROSITY

2. KEKUATAN EKAPAKSI (UCS)

3. PERMEABILITY4. ABRASIVENESS


74/78


75/78

HOW


76/78

PREEXISTING

ROCKS

BATUANMETAMORFIK

T, P, CHEMICAL

FLUIDS

METAMORFISME

CONTACT

REGIONAL/

DYNAMIC

CHANGES

TEXTURE

MINERALOGY

LINEATION

FOLIATION

NONFOLIATED

WHERE

HOW

WHERE

JENIS BATUAN& CIRI KEJU-

RUTERAAN

JENIS

PHASE DIAGRAM FOR WATER


77/78

PHASE DIAGRAM FOR WATER


78/78

NEXT LECTURE

MASA GEOLOGI

Batuan metamorfik.pptx

Documents

Transcript of Batuan metamorfik.pptx